Catalytic system which can be used for the stereospecific polymerization of α-olefins, process for this polymerization and polymers obtained

ABSTRACT

Catalytic system which can be used for the polymerization of α-olefins comprising: 
     a solid based on complexed titanium trichloride of δ crystalline form; 
     an organoaluminium compound; 
     an organic oxygenated silicon compound; 
     characterized in that the organoaluminium compound is a non-halogenated compound.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/424,611filed Apr. 19, 1995, abandoned which is a continuation of applicationSer. No. 08/056,779, May 4, 1993, now abandoned, the entire disclosuresof which are incorporated herein by reference.

The present invention relates to a catalytic system which can be usedfor the stereospecific polymerisation of α-olefins and to a process forthis polymerisation.

It is known to polymerise α-olefins using a catalytic system comprisinga solid constituent based on titanium trichloride and a cocatalystchosen from organic compounds of metals from groups Ia, IIa and IIIa ofthe Periodic Table (version published in Handbook of Chemistry andPhysics, 50th Edition).

Among the abovementioned catalytic systems, those which contain acatalytic solid based on complexed titanium trichloride of δ crystallineform and a dialkyl-aluminium halide, very particularly diethylaluminiumchloride, have a maximum activity and stereospecificity [K. Y. Choi andW. H. Ray, Rev. Macromol. Chem. Phys., C 25 (1), pg. 69-71 (1985) and P.C. Barbe, G. Cecchin, L. Noristi, Advances Polym. Sc., 81, pg. 19(1987)]. In practice, these systems contain a large excess ofdialkylaluminium halide with respect to the titanium compound [see forexamples in U.S. Pat. No. 4,210,738 which corresponds to the patentBE-A-780,758

The use of such catalytic systems has disadvantages however. Indeed, thepolymers which result therefrom contain a relatively large amount ofchlorinated residues arising essentially from the cocatalyst which, ifthey are not removed, confer a corrosive nature on these polymers anddetrimentally affect the stability thereof.

The use of non-halogenated cocatalysts would enable this problem to besolved but leads to resins being obtained which contain a largeproportion of amorphous polymer.

Attempts have been made to overcome this disadvantage by adding to thiscatalytic system a third constituent which is generally anelectron-donating compound and preferably an amino or organophosphoruscompound [Patent GB-A-1,486,194 (Imperial Chemical Industries)]. Theimprovement in stereospecificity which results therefrom is insufficientand is achieved to the detriment of the catalytic productivity.

It has now been found that the combination of certain catalytic solidsbased on complexed titanium trichloride, of δ crystalline form, with anon-halogenated organoaluminium cocatalyst and a specific thirdconstituent leads to halogen-poor catalytic systems which do not havethe disadvantages of the systems described earlier.

The present invention correspondingly relates to a catalytic systemwhich can be used for the polymerisation of α-olefins comprising atleast:

(a) one solid based on complexed titanium trichloride, of δ crystallineform;

(b) one organoaluminium compound;

(c) one organic oxygenated silicon compound; characterised in that theorganoaluminium compound is a non-halogenated compound.

In the present invention, organic oxygenated silicon compound [compound(c)] is understood to denote the silicon compounds in which the moleculecomprises at least one hydrocarbon group bonded via an oxygen atom.

These compounds (c) are most often chosen from the compounds representedby the general formula:

    R'.sub.n Si(OR").sub.4-n                                   (I)

in which

R' represents a hydrogen atom or a hydrocarbon radical containing from 1to 20 carbon atoms, chosen for example from alkyl, cycloalkyl, alkenyl,aryl, alkylaryl and arylalkyl radicals, which radicals can themselvescarry substituents such as amino groups. R' is preferably chosen fromalkyl, aryl and cycloalkyl radicals containing preferably from 1 to 18carbon atoms;

R" represents a hydrocarbon radical, identical to or different from R',containing from 1 to 12 carbon atoms and chosen for example from alkyl,cycloalkyl, alkenyl, aryl, alkylaryl and arylalkyl radicals, whichradicals can themselves be substituted by groups such as alkoxy groups.Preferably, R" is chosen from alkyl and aryl radicals containing from 1to 8 carbon atoms;

n is an integer such that 0≦n≦3.

In the compounds (C), the n radicals R' and the (4-n) radicals R" caneach, independently of each other, represent identical or differentorganic radicals. Moreover, the catalytic systems according to theinvention can contain one or more compounds (c).

Examples of organic silicon compounds (c) which can be used in thecatalytic systems according to the invention are tetra-, tri- anddimethoxysilanes and tetra-, tri- and diethoxysilanes, optionallysubstituted by alkyl, cycloalkyl or aryl radicals, which are identicalor different, chosen for example from methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, tert-butyl, n-amyl, isoamyl, cyclopentyl,n-hexyl, cyclohexyl or phenyl radicals.

The compounds (c) preferentially used in the catalytic systems accordingto the invention are compounds corresponding to the formula (I) whichcontain one or two substituents (OR") in which the radicals R", whichare identical or different, are chosen from hydrocarbon radicalscontaining from 1 to 3 carbon atoms and at least one substituent R'chosen from alkyl and cycloalkyl radicals containing at least onesecondary or tertiary carbon atom. The compounds (c) which have giventhe best results are dimethoxy- and diethoxysilanes substituted by atleast one alkyl or cycloalkyl radical containing a secondary or tertiarycarbon atom in the α, β or γ position.

As examples of such compounds (c), there may be mentioneddiisobutyldimethoxysilane, di(tert-butyl)dimethoxysilane,diisopropyldimethoxysilane, dicyclohexyldimethoxysilane,cyclohexylmethyldimethoxysilane or isobutylmethyldimethoxysilane.

The catalytic systems according to the invention additionally contain anon-halogenated organoaluminium compound [compound (b)] corresponding tothe formula:

    AlR.sub.m Y.sub.3-m                                        (II)

where:

R represents a hydrocarbon radical, containing from 1 to 18 carbon atomsand preferably from 1 to 12 carbon atoms chosen from alkyl, aryl,arylalkyl, alkylaryl and cycloalkyl radicals;

Y represents a group chosen from --OR¹, --SR¹ and --NR¹ R² in which R¹and R² each represent an identical or different hydrocarbon radicalchosen from alkyl, aryl, arylalkyl, alkylaryl and cycloalkyl radicalspreferably containing from 1 to 20 carbon atoms;

m is a number such that 0<m≦3.

As examples of compound (b) which can be used in the catalytic systemsaccording to the invention, there may be mentioned trialkylaluminiumssuch as, for example, trimethylaluminium, triethylaluminium,tripropylaluminium, triisopropylaluminium, tributylaluminium,triisobutylaluminium, trihexylaluminium, trioctylaluminium ortridodecylaluminium, and alkoxyalkylaliminiums such as, for example,diethylethoxyaluminium.

Non-halogenated organoaluminium compounds (b) which can also be used inthe catalytic systems according to the invention are aluminoxane-typeoligomers existing in the cyclic and/or linear form which can berepresented by the general formulae: ##STR1## and

    (R).sub.2 Al--O--[Al(R)--O].sub.n',--Al(R).sub.2           (IV)

in which R has the meaning given above for formula (II) and n' is aninteger generally between 2 and 50. As examples of compound (b) offormula (III) and (IV), there may be mentioned methyl, ethyl, andbutylaluminoxanes.

It is obvious that the catalytic systems according to the invention maycontain one or more compounds (b).

The compounds (b) are preferably chosen from trialkylaluminiums andalkylalkoxyaluminiums and their mixtures.

The most outstanding catalytic systems contain, as compounds (b), atrialkylaluminium or a mixture of trialkylaluminiums. Finally,trialkylaluminiums in which the alkyl radicals contain more than twocarbon atoms have the advantage of being able to be used over a widerange of aluminium of compound (b)/titanium of compound (a) ratioswithout variations in the properties of the polymers which resulttherefrom being observed.

Besides the organoaluminium compound (b) and the organic oxygenatedsilicon compound (c), the catalytic systems according to the inventioncomprise a catalytic solid based on complexed titanium trichloride, of δcrystalline form [compound (a)]. In the context of the presentinvention, compound (a) is understood to denote catalytic solids basedon complexed titanium trichloride, of δ crystalline form, essentiallyfree of magnesium, obtained by processes involving a reduction of atitanium compound by an organoaluminium reducing agent. These catalyticsolids based on titanium trichloride belong to the δ crystalline form asdefined, for example, in Journal of Polymer Science, 51, pages 399-410(1961). Such solids are generally purple in colour.

According to the present invention, there are preferably used two typesof compound (a) which can be characterised by their method of production[compounds (a1) and (a2)].

Compound (a1) which can be used in the catalytic systems according tothe invention is obtained by successive or combined treatments of thesolids resulting from the reduction of titanium tetrachloride ortetraalkoxide by an organoaluminium reducing agent (1), by anelectron-donating compound (2) and by a halogenated compound (3).

Organoaluminium reducing agents (1) which can preferably be used forproducing the constituent (a1) are compounds which contain at least onehydrocarbon radical attached directly to the aluminium atom. Examples ofcompounds of this type are mono-, di- and trialkylaluminiums in whichthe alkyl radicals contain from 1 to 12, preferably from 1 to 6, carbonatoms, such as alkylaluminium chlorides, trialkylaluminiums andalkylalkoxyaluminiums. As examples of these compounds, there may bementioned diethylaluminium chloride, triethylaluminium,isoprenylaluminiums, diisobutylaluminium hydride, diethylethoxyaluminiumand ethylaluminium sesquichloride. The best results are obtained withdialkylaluminium chlorides and, in particular, with diethylaluminiumchloride.

The electron-donating compound (2) is preferably chosen from the familyof the aliphatic ethers, and more particularly from those in which thealiphatic radicals each comprise from 2 to 8 carbon atoms, preferablyfrom 4 to 6 carbon atoms. A typical example of an aliphatic ether givingvery good results is diisoamyl ether. Di(n-butyl) ether is equallysuitable.

The halogenated compound (3) is chosen from inorganic halogenatedcompounds, organic halogenated compounds, interhalogen compounds andhalogens. Among these compounds (3), there may be mentioned:

as inorganic halogenated compounds: metal and nonmetal halides, such astitanium or silicon halides for example and more particularly titaniumtetrachloride;

as organic halogenated compounds: halogenated hydrocarbons such ashalogenated alkanes and carbon tetrahalides for example and moreparticularly hexachloroethane;

as interhalogen compounds: the chlorides and bromides of iodine forexample;

as halogen: chlorine, bromine or iodine.

Organic and inorganic halogenated compounds are suitable.

The best results were obtained with inorganic halogenated compounds andin particular with titanium tetrachloride.

Preferably, the treatment by means of the halogenated compound (3) iscarried out following upon the treatment by means of theelectron-donating compound and is most often carried out in the presenceof a residual amount of the latter. This residual amount can result froma partial removal from the solution used during the treatment with theelectron-donating compound or from a supplementary addition ofelectron-donating compound during the treatment by means of thehalogenated compound.

The stages and treatments for the preparation of compound (a1) describedabove can be carried out in an inert hydrocarbon diluent generallychosen from the liquid aliphatic, cycloaliphatic and aromatichydrocarbons, such as liquid alkanes, cycloalkanes or isoalkanes, orbenzene. The mixtures of these diluents are equally suitable.

Compounds (a1) of this type which are particularly suitable forformation of the catalytic systems according to the invention aredescribed in U.S. Pat. No. 4,210,738 which corresponds to the patentBE-A-780,758, the contents of which are incorporated for reference inthe present description.

At any point during its preparation, after the reduction stage or aftertreatment with the electron-donating compound (2) or after treatmentwith the halogenated compound (3), but preferably after the reductionstage, the solid based on TiCl₃ can be subjected to a treatment whichaims at reducing the friability of its constituent particles. Thistreatment, called "prepolymerisation", consists in bringing the solidinto contact with an α-olefin, such as for example propylene orethylene, under polymerising conditions so as to obtain a solidgenerally containing from approximately 5 to approximately 500% byweight of "prepolymerised" α-olefin with respect to the weight oftitanium trichloride.

The catalytic solid based on complexed titanium trichloride of δcrystalline form of type (a1) can also be activated by bringing it intocontact with an activation agent so as to maintain the stability thereofand/or to increase the stereospecifity thereof. This activationtreatment consists in bringing the solid based on complexed titaniumtrichloride of δ crystalline form, preferably separated from the mediumin which it was prepared and washed with an inert hydrocarbon diluent asdefined above, into contact with an activation agent chosen fromorganoaluminium compounds and the products of the reaction of anorganoaluminium compound with a compound chosen from hydroxyaromaticcompounds in which the hydroxyl group is sterically blocked. Theorganoaluminium compound is preferably chosen from trialkylaluminium andalkylaluminium chlorides. Among these compounds, the best results areobtained with triethylaluminium and diethylaluminium chloride. Thehydroxyaromatic aromatic compound in which the hydroxyl group issterically blocked is preferably chosen from phenols which aredi(tert-alkylated) in the positions also with respect to the hydroxylgroup and the esters of3-(3',5'-di(tert-butyl)-4'-hydroxyphenyl)propionic acid. Among thesecompounds, the best results were obtained with 2,6-di(tert-butyl)-4-methylphenol and n-octadecyl3-(3',5'-di(tert-butyl)-4'-hydroxyphenyl)propionate.

Other details with respect to the additional activation treatmentsdefined above, especially the nature of the organoaluminium andhydroxyaromatic compounds and the operating conditions under which theyare carried out are described in U.S. Pat. No. 4,210,729 whichcorresponds to the patent BE-A-803,875 (Solvay), the contents of whichare incorporated for reference in the present application.

Activated compounds (a1) leading to the best results are those resultingfrom the method of preparation described in the patent applicationEP-A-261,727. These constituents result from the activation treatment ofthe catalytic solids based on complexed titanium trichloride of δcrystalline form of type (a1) obtained according to U.S. Pat. No.4,210,738 which corresponds to the patent BE-A-780,758 above and whichhave preferably been subjected to the prepolymerisation treatment.

When the catalytic systems according to the present invention contain acatalytic solid based on titanium trichloride of δ crystalline form oftype (a1), having or not having been subjected to the activation and/orprepolymerisation treatment, the amounts of compounds (a1), (b) and (c)used are generally such that the molar ratio of the aluminium of thecompound (b) to the titanium of the compound (a1) varies from 1 to 50.These amounts are additionally such that the molar ratio of thisaluminium to the silicon of the compound (c) varies from 0.1 to 50. Inparticular, good results are obtained when the molar ratio of thealuminium of (b) to the titanium of (a1) is greater than or equal toapproximately 1.5 and more particularly greater than or equal toapproximately 2. The smaller ratio is additionally most often less thanor equal to approximately 25 and preferably less than or equal toapproximately 20. The catalytic systems of this type which show goodresults generally have a molar ratio of the aluminium of the compound(b) to the silicon of the compound (c) which is greater than or equal toapproximately 1, preferably greater than or equal to approximately 1.5.This ratio is most often less than or equal to approximately 10 andpreferably less than or equal to approximately 5.

The catalytic systems according to the invention can also contain, ascatalytic solid based on complexed titanium trichloride of δ crystallineform, a compound (a2) obtained by heat treatment, in the presence of ahalogenated agent (3) as defined above, of the liquid material resultingfrom bringing TiCl₄, pretreated with an electron-donating compound (2)also as defined above, into contact with a composition (0) correspondingto the general formula:

    AlR.sub.p Z.sub.q X.sub.3-(p+q)                            (V)

in which

R represents a hydrocarbon radical as defined above with respect toformula (II);

Z represents a group chosen from --OR⁴, --SR⁴ and --NR⁴ R⁵ in which R⁴and R⁵ each represent a hydrocarbon radical or a hydrogen atom;

X represents a halogen atom;

p is any number such that 0<p<3;

q is any number such that 0<q<3;

the sum (p+q) being such that 0<(p+q)≦3.

In formula (V), X is preferably chlorine; R is preferably chosen fromlinear or branched alkyl radicals containing from 2 to 8 carbon atoms; Zis preferably chosen from groups --OR⁴ in which R' is a linear orbranched alkyl radical containing from 1 to 12 carbon atoms or anoptionally substituted aryl radical containing from 6 to 35 carbonatoms. A very particularly preferred radical R is the ethyl radical.Very particularly preferred radicals R⁴ are ethyl and amyl radicals suchas the iso- and n-amyl radicals.

In formula (V), p is preferably a number such that 1≦p≦2 and qpreferably a number such that 0.1≦q≦2.

The compositions (0) can be defined chemical compounds or mixtures ofcompounds. The formula (V) must thus be considered as an empiricalstructural formula representing said compounds or, in the case ofmixtures, representing the average composition of the latter.

The compositions (0) can be prepared by bringing:

an organoaluminium compound (A) of general formula:

    AlR.sub.r X.sub.3-r                                        (VI)

into contact with

a compound (B) chosen from the compounds of general formula:

    AlR.sub.t Z.sub.t, X.sub.3-(t+t')                          (VII);

    ZH                                                         (VIII);

and

the aluminoxane-type oligomers of formula (III) and (IV) in proportionssuitable for producing a composition (0) corresponding to the formula(V) above.

In the formulae (VI), (VII) and (VIII) above, R, Z and X respectivelyhave the meanings given above with regard to the formula (V). In theformula (VI), r is any number such that 0<r≦3 and, in the formula (VII),t is any number such that 0≦t<3 and t' is any number such that 0<t'≦3,the sum (t +t') being such that 0<(t+t')≦3.

Preferred compounds (A) are dialkylaluminium chlorides, veryparticularly diethylaluminium chloride. The preferred compounds (B) offormula (VII) are alkylalkoxyaluminiums and their chlorides, veryparticularly diethylethoxyaluminium and ethylethoxy- andethylisopentoxyaluminium monochlorides. As examples of compounds (B) offormula (VIII), there may be mentioned alcohols, thioalcohols, phenols,thiophenols and secondary amines. Very particularly preferred compounds(B) of formula (VIII) are aliphatic alcohols and in particular ethanoland iso- and n-amyl alcohols.

A particularly preferred and simple procedure for the preparation of thecomposition (0) comprises bringing a compound (A), such as an alkylatedaluminium compound, into contact with a compound (B), such as analiphatic alcohol, in a ratio of the aluminium contained in the compound(A) to the hydrocarbon radical contained in the compound (B) of between1:0.1 and 1:3.

Another method of preparation giving good results comprises bringing acompound (A), such as an alkylated aluminium compound, into contact withthe compound (B), such as an alkylalkoxyaluminium, in a ratio of thealuminium contained in the compound (A) to the alkoxy radical containedin the compound (B) of between 1:0.1 and 1:10.

For the preparation of the compounds (a2) which can be used in thecatalytic systems according to the present invention, the composition(0) is brought into contact with TiCl₄, itself pretreated with anelectron-donating compound (2) as defined above. A typical example of anelectron-donating compound (2) giving very good results is here alsodiisoamyl ether. Di(n-butyl) ether is equally suitable.

The molar ratio of TiCl₄ to the electron-donating agent (2) can varywithin wide limits. It generally varies from 0.01 mol to 20 mol of TiCl₄per mole of electron-donating compound.

The general conditions for bringing TiCl₄, pretreated with theelectron-donating compound as described above (hereafter more brieflycalled "pretreated TiCl₄ "), into contact with the composition (0) arenot critical provided that they lead to the formation of a substantiallyhomogeneous and solid-free liquid material. The composition (0) andpretreated TICl₄ are brought into contact in respective amounts suchthat an at least partial reduction of the TiCl₄ takes place withoutconcomitant substantial production of solid precipitate. To this end,the amount of composition (0) brought into contact with pretreated TiCl₄is such that the atomic ratio of the aluminium contained in thecomposition (0) to the titanium contained in pretreated TiCl₄ isgenerally from 0.05 to 10, preferably from 0.2 to 2. The temperature atwhich the composition (0) and pretreated TiCl₄ are brought into contactgenerally varies from 0 to 60° C., preferably from 10 to 40° C.

For the preparation of the catalytic solids according to the invention,the liquid material obtained as shown above must be converted to solidparticles. To this end, the said material is subjected to a heattreatment, generally lasting from 5 to 150 minutes, in the presence of ahalogenated compound (3) as defined above so as to induce thesubstantial precipitation of solid particles based on complexed titaniumtrichloride.

To this end, the liquid material is gradually brought, continuously orin a succession of stages, to a temperature which does not exceed theboiling point of the liquid material and which most often varies from 80to 120° C.

The preferred halogenated compound (3) for the preparation of thecompounds (a2) is titanium tetrachloride. It can be added to the liquidmaterial at any time during the heat treatment.

In particular, when TiCl₄ is used as the halogenated compound (3), thisTiCl₄ can advantageously arise from an unreduced excess of initial TiCl₄from which the catalytic solids according to the invention are prepared.

The amount of halogenated compound (3) used, expressed with respect tothe amount of titanium trichloride present in the liquid material, isgenerally from 0.1 to 20 mol of halogenated compound (3) per moletitanium trichloride.

The solid particles thus obtained can then be subjected to a maturinggenerally carried out at the temperature reached at the end of the heattreatment, then preferably separated from their preparation medium andoptionally washed by means of an inert hydrocarbon diluent as describedabove and which can also be used for preparing the solid based oncomplexed titanium trichloride [compound (a2)].

Other details with respect to the operating conditions under which thesynthesis of the compound (a2) is carried out are described in U.S. Pat.No. 5,206,198 which corresponds to Belgian Patent Application 9,001,054,filed on Nov. 8, 1990, the contents of which are incorporated forreference in the present description.

The compound (a2) thus obtained is formed of solid particles ofcomplexed titanium trichloride of δ crystalline form, with a generallypurple colour, with a substantially spherical general shape, with anarrow particle size distribution and with a mean diameter of between 5and 150 μm. Its titanium trichloride content is generally greater than50% of its weight and its content of electron-donating compound isgenerally less than 15% by weight with respect to the total weight ofthe particles.

The porosity of the particles of compounds (a2) depends on the choice ofthe operating conditions of their preparation. It has thus beenobserved, in particular, all other conditions remaining substantiallyunchanged, that increasing the content of Z groups in the composition(0) leads to a modification of the porosity of the particles ofcatalytic solid and in particular to an increase in the internal porevolume of these particles generated by pores whose radii vary from 1000to 15,000 Å (hereafter more simply called IPV). By virtue of the processof manufacture of the catalytic solids according to the invention, it isthus possible to adjust their porosity, especially the IPV, from valuesas low as approximately 0.02 cm³ /g to values as high as approximately0.4 cm³ /g.

The use, in the catalytic systems according to the invention, ofcompounds (a2) of high porosity is particularly suitable for themanufacture of highly impact-resistant sequential copolymers obtained byincorporating, in a propylene polymer prepared in a first stage, largeamounts of a propylene elastomer prepared in a second stage.

Indeed, the increase in the porosity of the compounds (a2) in the regionof the pore radii described above leads especially to α-olefin polymersof increasing porosity, which makes it possible to incorporate thereinlarge and increasing amounts of elastomeric products withoutencountering adhesion problems.

Another advantage of the use of these compounds (a2) is that they leadto polymers in which the incorporation of additives such as pigments orstabilising agents is particularly easy.

Various variations can be introduced into this process for producing thecompound (a2) without departing from the context of the latter.

A first implementational variation (i) consists in adding, to the mediumfor the preparation of the catalytic solid based on complexed TiCl₃, atany time but preferably before the heat treatment of the liquidmaterial, an organic or inorganic support (S) having a porous texturesuch that the solid particles based on complexed titanium trichlorideare deposited at the surface of the support (S) or precipitate insidethe pores of the latter.

As examples of support (S), there may be mentioned preformed polymers,oxides of silicon, aluminium, magnesium, titanium or zirconium, andmixtures of these oxides.

A second implementational variation (ii) consists in subjecting thecatalytic solid particles based on complexed titanium trichloride of δcrystalline form, optionally prepared in the presence of the support(S), to a prepolymerisation treatment as described above with respect tothe compounds of type (a1).

A third implementational variation (iii) consists in subjecting thesecatalytic solid particles based on complexed titanium trichloride,optionally prepared in the presence of the support (S), to an activationtreatment identical to that described above for producing theconstituents (a1).

It is also possible to combine the variations (ii) and (iii) describedabove, that is to say to subject the catalytic solid particles,optionally prepared in the presence of the support (S), to theadditional activation treatment simultaneously with the"prepolymerisation" treatment.

It is also possible to combine the variations (ii) and (iii) by carryingthem out successively.

Details relating to these variations can also be found in U.S. Pat. No.5,206,198 which corresponds to the patent application BE-A-9,001,054.

When the catalytic systems according to the present invention contain acompound (a2) as solid based on complexed titanium trichloride of δcrystalline form, the amounts of compounds (a2), (b) and (c) used aregenerally such that the molar ratio of the aluminium of (b) to thetitanium of (a2) varies from 1 to 50. These conditions are additionallysuch that the molar ratio of the aluminium of (b) to the silicon of (c)varies from 0.1 to 50. In particular, good results are obtained when themolar ratio of the aluminium of (b) to the titanium of (a2) is greaterthan or equal to approximately 1.5 and more particularly greater than orequal to approximately 2. This molar ratio is additionally most oftenless than or equal to approximately 25, preferably less than or equal toapproximately 20. The catalytic systems of this type showing goodresults generally have a molar ratio of the aluminium of the compound(b) to the silicon of the compound (c) which is greater than or equal toapproximately 1 and preferably greater than or equal to approximately1.5. This ratio is most often less than or equal to approximately 10 andpreferably less than or equal to approximately 5.

It is possible to use high molar ratios of aluminium to silicon when itis desired to produce polymers having poorer isotacticities. Thesepolymers are generally obtained by using molar ratios of the aluminiumof (b) to the silicon of (c) which are greater than approximately 4. Inthis case, this ratio is generally less than or equal to approximately30 and preferably less than or equal to approximately 25. Polymerisationprocesses which are particularly well suited for producing thesepolymers having poorer isotacticity are the gas phase polymerisationprocesses.

The catalytic systems thus defined are applied to the polymerisation ofolefins having end unsaturation such as α-olefins in which the moleculecontains from 2 to 18 and preferably from 2 to 6 carbon atoms and inparticular ethylene, propylene, 1-butene, 1-pentene, 1-methylbutenes,hexene or 3- and 4-methyl-1-pentenes.

Consequently, the present invention also relates to a process for homo-and/or copolymerisation using one or more of the monomers mentionedabove under polymerisation conditions in the presence of one or theother of the catalytic systems described above. A particularlyadvantageous polymerisation process relates to the stereospecificpolymerisation of propylene, 1-butene and 4-methyl-1-pentene tocrystalline polymers. The catalytic systems are also applied to thecopolymerisation of these α-olefins with at least one non-identicalcomonomer chosen from the α-olefins as described above and diolefinscomprising from 4 to 18 carbon atoms. The diolefins are preferablynon-conjugated aliphatic diolefins such as 1,4-hexadiene, non-conjugatedmonocyclic diolefins such as 4-vinylcyclohexene, alicyclic diolefinshaving an endocyclic bridge such as dicyclopentadiene or methylene- andethylidenenorbornene and conjugated aliphatic diolefins such asbutadiene or isoprene.

They are also applied to the manufacture of so-called block copolymerswhich are made starting from α-olefins and/or diolefins. These blockcopolymers consist of distinct blocks of variable composition; eachblock consists of a homopolymer of an α-olefin or of a statisticalcopolymer comprising an α-olefin and at least one comonomer chosen fromα-olefins and diolefins. The α-olefins and diolefins are chosen fromthose mentioned above.

The catalytic systems according to the invention are particularly wellsuited for the manufacture of copolymers of propylene and of copolymersof the latter containing in total at least 50% by weight of propyleneand preferably at least 60% by weight of propylene.

Generally, in this case, the polymerisation temperature varies from 20to 200° C. and preferably from 50 to 100° C., the best results beingobtained from 65 to 95° C. The pressure is generally chosen betweenatmospheric pressure and 60 atmospheres and preferably from 10 to 50atmospheres. This pressure can depend on the temperature at which thepolymerisation is carried out.

The polymerisation can be carried out continuously or noncontinuously.

The polymerisation can be carried out according to any known process: insolution or in suspension in an inert hydrocarbon diluent, such as thosedefined with respect to the preparation of the compounds (a). Thediluent preferably used during the polymerisation is generally chosenfrom butane, isobutane, hexane, heptane, cyclohexane, methylcyclohexaneor their mixtures. It is also possible to carry out the polymerisationin the monomer or in one of the monomers maintained in the liquid stateor even in the gaseous phase.

The amount of the various compounds of the catalytic systems accordingto the invention used for this polymerisation is not critical providedthat the ratios between the various compounds (a), (b) and (c) arerespected. The polymerisation is generally carried out so that the totalamount of organometallic compound (b) is greater than 0.1 mmol per litreof diluent, of liquid monomer or of reactor volume and preferablygreater than or equal to 0.5 mmol per litre.

The compounds (a), (b) and (c) are generally added separately to thepolymerisation medium. The order of introduction of these compounds isnot critical. However, it may prove advantageous to introduce compound(a) last.

A precontact can also be carried out between compound (b) and compound(c) or between compound (a) and one or the other of compounds (b) and(c), or between these three compounds before using them for thepolymerisation.

Such a precontact is generally carried out at a variable temperature of-40 to +80° C. for a period of time which depends on this temperatureand which can range from a few seconds to a number of hours or even anumber of days.

However, when the precontact involves compound (a), it is preferable tolimit the period of time of precontact to a few seconds or even a fewminutes.

The mean molecular mass of the polymers manufactured according to theprocess according to the invention can be adjusted by the addition tothe polymerisation medium of one or more agents for adjusting the meanmolecular mass, such as hydrogen, diethylzinc, alcohols, ethers andalkylhalides. Hydrogen is quite suitable.

The catalytic systems according to the invention can preferably used forthe production, with particularly high yields, of propylene polymershaving a wide stereospecificity range.

Additionally, the catalytic systems are particularly well suited to thepolymerisation of propylene at high temperature. Under these conditions,particularly high polymerisation yields are observed with insignificantreduction in the stereospecificity.

The use of the catalytic systems according to the invention makes itpossible to produce, with good yields, polymers containing a loweramount of chlorine than that measured on polymers resulting fromconventional catalytic systems based on titanium trichloride. For thisreason, the polymers obtained are more stable and their use does notlead to corrosion of the devices used for this purpose. Additionally,the stabilisation of these polymers requires smaller amounts ofadditives, which constitutes not only an economic advantage but alsomakes it possible to use the said polymers in applications where a highpurity is required.

The catalytic systems according to the invention also make it possible,when they are used in gas phase polymerisation processes, to avoid theformation, in the polymerisation reactor or in the device forcirculating the gaseous monomers, of low molecular mass polymersexisting in the form of viscous or semi-solids oils capable ofdisturbing the smooth operation of the polymerisation reactor. Such ause of the catalytic systems according to the invention is consequentlyparticularly favourable.

Finally, the catalytic systems according to the invention make itpossible to produce, with very good yields, propylene polymers of veryhigh mean molecular mass. According to the present invention, propylenepolymers of very high molecular mass is understood to mean propylenepolymers of which the mean molecular mass by weight (M_(W)) is at least8·10⁵ g/mole. The mean molecular mass by weight is preferably greaterthan 1.0·10⁶ g/mole and can reach values as high/as 1.2·10⁶ g/mole.Propylene polymers of this type capable of being obtained under thepolymerisation processes according to the invention are propylenehomopolymers as well as propylene copolymers as defined above. Thesepolymers are obtained with good yields in the various polymerisationprocesses when the polymerisation medium does not contain an agent foradjusting the molecular mass.

The following examples are used to illustrate the invention.

The meaning of the symbols used in these examples, the units expressingthe quantities mentioned and the methods for measuring these quantitiesare explained below.

IPV=internal pore volume of the catalytic solid measured in the regionof the pore radii of between 1000 and 15,000 Å and expressed in cm³ /g,measured by the mercury penetration method using porosimeters marketedby the firm Carlo Erba Co.

act.=catalytic activity expressed conventionally in grams of polymerobtained per hour and per gram of TiCl₃ contained in the catalyticsolid. This activity is estimated indirectly from the determination byX-ray fluorescence of the residual titanium content in the polymer.

AD=the apparent density of the insoluble polymer expressed in g/dm³.

fTri=isotacticity index of the polymer, estimated by the molar fractionof isotactic triads (sequenced chain of three propylene monomer units inmeso configuration) in the overall polymer. This value is determined by¹³ C nuclear magnetic resonance as described in Macromolecules, Volume6, No. 6, pages 925-926 (1973) and in references (3) to (9) of thispublication.

I.I.=isotacticity index of the polymer, estimated by that fraction ofthe latter, expressed as a % by weight in respect to the total amount ofpolymer collected, which is insoluble in boiling heptane.

MFI=melt flow index measured with a load of 2.16 kg at 230° C. andexpressed in g/10 min (ASTM standard D 1238).

η=intrinsic viscosity of the polymer measured in solution in tetralin at140° C. and expressed in g/dl.

M_(W) =mean molecular mass by weight expressed in g/mol and measured bysteric exclusion chromatography in 1,2,4-trichlorobenzene at 135° C. ona Waters type 150C chromatograph.

TEAL=triethylaluminium.

TBAL=tributylaluminium.

DIBDMS=diisobutyldimethoxysilane.

nPTMS=n-propyltrimethoxysilane.

DPDMS=diphenyldimethoxysilane.

Et=ethyl radical or C₂ H₅ --.

Isoamyl=isoamyl radical or (CH₃)₂ CH--CH₂ --CH₂ --.

EXAMPLE 1

Example 1 illustrates a catalytic system according to the inventioncontaining, as solid based on complexed TiCl₃ of δ crystalline form, acompound (a1) which has not been subjected to any prepolymerisation oractivation treatment.

A--Preparation of Compound (a1)

90 ml of dry hexane and 60 ml of pure TiCl₄ are introduced, under anitrogen atmosphere, into an 800 ml reactor equipped with a 2-bladedstirrer rotating at 400 revolutions/min. This hexane/TiCl₄ solution iscooled to 0(±1) ° C. A solution of 190 ml of hexane and 70 ml ofdiethylaluminium chloride (DEAC) is added thereto over 4 h whilemaintaining the temperature of 0 (±1)° C. in the reactor.

After addition of the DEAC/hexane solution, the reaction mixture,consisting of a suspension of fine particles, is kept stirring at 1(±1)° C. for 15 min, is then brought over 1 h to 25° C., maintained for1 h at this temperature and then brought over approximately 1 h to 65°C. The mixture is kept stirring for 2 h at 65° C.

The liquid phase is then separated from the solid and the solid iswashed with dry hexane.

The reduced solid thus obtained is suspended in 456 ml of diluent(hexane) and 86 ml of diisoamyl ether (DIAE) are added thereto. Thesuspension is stirred at 250 rev/min for 1 h at 50° C. and then allowedto settle. After having removed the supernatant, the solid isresuspended in 210 ml of hexane and 52 ml of TiCl₄ are added thereto.The suspension is then kept stirring (150 rev/min) at 75° C. for 2 h.The liquid phase is then removed by filtration and the solid based oncomplexed titanium trichloride is washed with dry hexane and then driedin a fluidised bed under nitrogen at 70° C.

The catalytic solid thus obtained, which is purple in colour, contains,per kg, 875 g of TiCl₃ of δ crystalline form and 85 g of DIAE.

B--Polymerisation of Propylene in Suspension in the Liquid Monomer(Reference Conditions)

The following are introduced, while purging with dry nitrogen, into a 51 autoclave which has been dried beforehand:

228 mg (2mmol) of TEAL (in the form of a 200 g/l solution in hexane);

176.8 mg of DIBDMS (in the form of a 0.384 mol/l solution in hexane):

59 mg of compound (a1) as prepared in Stage A;

a hydrogen pressure of approximately 1 bar;

3 1 of liquid propylene;

so that the molar ratio of the aluminium of the TEAL to the titanium ofcompound (a1) is equal to 6 and that the molar ratio of the aluminium ofthe TEAL to the silicon of the DIBDMS is equal to 2.3.

The reactor is maintained at 80° C. with stirring for 2 hours. Theexcess propylene is then degassed and the polymer formed recovered,being 664 g of dry polypropylene containing 18 ppm of titanium, 40 ppmof chlorine and having the following characteristics:

AD=467;

fTri=93;

I.I.=96.3;

MFI=0.44.

The α activity of compound (a1) is 8626.

Comparative Example 2R

This example illustrates polymerisation of propylene by means of acatalytic system containing 70 mg of compound (a1) described in Example1 and 480 mg of diethylaluminium chloride (DEAC).

The polymerisation test in liquid propylene (3 h, 80° C.) makes itpossible to obtain, with an activity of 3700, a polymer containing 28ppm of titanium; 270 ppm of chlorine and having the followingcharacteristics:

AD=480;

I.I.=95.8;

MFI=2.5.

Comparison of this example and Example 1 shows clearly that thecatalytic systems according to the invention are particularly active.Moreover, the catalytic systems according to the invention lead, atequal productivity, to a polymer containing less chlorine by a factor ofapproximately 4.3.

EXAMPLES 3 to 10R

The following Examples 3 to 10R illustrate catalytic systems containingcompounds (a1) which have been subjected to prepolymerisation and anactivation treatment. Examples 3 to 9 are carried out according to theinvention. Example 10R is a comparative example.

EXAMPLES 3 and 4

A--Preparation of compound (a1)

A solid based on complexed titanium trichloride is prepared as describedin Example 1. However, after treating the reduced solid suspension withstirring for 2 hours at 65° C. and cooling to approximately 550° C.,propylene is introduced under a pressure of 2 bars into the head spaceof the reactor. This introduction is continued for a sufficient time(approximately 45 min) to obtain, per kg of final solid, 65 g ofpolymerised propylene. The suspension of thus prepolymerised solid isthen cooled to 400° C. and washed with dry hexane. The preparation isthen continued as shown in Example 1, Part A.

The solid based on complexed TiCl₃ thus obtained is then resuspended inhexane (at a concentration of 4 ml of hexane per gram of solid) andbrought into contact with 120 ml of a solution containing, per litre ofhexane, 80 g of DEAC and 176.2 g of n-octadecyl3-(3',5'-di(tert-butyl)-4'-hydroxyphenyl)propionate marketed under thename Irganox 1076 by Ciba-Geigy.

The suspension with the added solution is kept stirring for 1 hour at30° C.

After settling, the resulting activated catalytic solid is washed withdry hexane, with resuspension of the solid.

The activated catalytic solid thus obtained contains, per kg, 720 g ofTiCl₃ and 40 g of DIAE.

B--Polymerisation of Propylene in Suspension in the Liquid Monomer

The characteristics of the catalytic systems used are shown in Table I,as well as the results of the polymerisation tests (referenceconditions) carried out in the presence of this compound (a1).

                  TABLE I                                                         ______________________________________                                        Examples          3       4                                                   ______________________________________                                        Catalytic systems                                                             compound (b)      TEAL                                                        compound (c)      DIBDMS                                                      quantity of (b) (mmol)                                                                          2       2                                                   Al/Ti molar ratio 4.6     11.4                                                Al/Si molar ratio 1.8     2.0                                                 Polymerisation results                                                        act.              9703    6750                                                AD                502     494                                                 fTri              92      93                                                  I.I.              97.9    97.4                                                MFI               0.2     1.7                                                 Cl in the polymer (ppm)                                                                         36      51                                                  ______________________________________                                    

EXAMPLE 5

Example 5 illustrates the production of high molecular weightpolypropylene by means of compound (a1) described in Example 3.Polymerisation is carried out under the conditions of Example 1, Part Bbut with the polymerisation temperature being maintained at 65° C. for 2h and with no introduction of hydrogen. The characteristics of this testare shown in Table II below.

                  TABLE II                                                        ______________________________________                                        Examples         5                                                            ______________________________________                                        Catalytic systems                                                             compound (b)     TEAL                                                         compound (c)     DIBDMS                                                       quantity of (b) (mmol)                                                                         2                                                            Al/Ti molar ratio                                                                              8.6                                                          Al/Si molar ratio                                                                              2.0                                                          Polymerisation results                                                        act.             5544                                                         AD               490                                                          fTri             90                                                           I.I.             95.8                                                         MFI              non-measurable                                               η            1.07                                                         M.sub.w          1,175,000                                                    ______________________________________                                    

EXAMPLE 6 and 7

These examples illustrate the use of various silicon compounds inpolymerisation tests as described in Example 5 (65° C.-2 h) butintroducing approximately 1 bar of hydrogen.

The composition of the catalytic systems and the results of thepolymerisation tests are shown in Table III below.

                  TABLE III                                                       ______________________________________                                        Examples         6        7                                                   ______________________________________                                        Catalytic systems                                                             compound (b)     TEAL     TEAL                                                compound (c)     DIBDMS   DPDMS                                               quantity of (b) (mmol)                                                                         2        2                                                   Al/Ti molar ratio                                                                              6.5      7.3                                                 Al/Si molar ratio                                                                              2.0      2.0                                                 Polymerisation results                                                        act.             4704     3528                                                AD               472      436                                                 fTri             92       91                                                  I.I.             95.2     93.8                                                MFI              3.7      2.8                                                 ______________________________________                                    

EXAMPLES 8 and 9

These examples illustrate the polymerisation of propylene by means ofcatalytic systems containing a trialkylaluminium [compound (b)] in whichthe alkyl radicals contain more than 2 carbon atoms.

The characteristics of these catalytic systems and the results of thepolymerisation tests carried out under the conditions of Example 1, PartB are shown in Table IV below.

                  TABLE IV                                                        ______________________________________                                        Examples          8        9                                                  ______________________________________                                        Catalytic systems                                                             compound (b)      TBAL     TBAL                                               compound (c)      DIBDMS   DIBDMS                                             quantity of (b) (mmol)                                                                          2        2                                                  Al/Ti molar ratio 8.5      15                                                 Al/Si molar ratio 3.3      3.2                                                Polymerisation results                                                        act.              10720    11516                                              AD                498      487                                                fTri              90       89                                                 I.I.              96.6     95.5                                               MFI               0.6      1.9                                                Cl in the polymer (ppm)                                                                         32       30                                                 ______________________________________                                    

EXAMPLE 10R

Example 10R illustrates the polymerisation of propylene under conditionsidentical to those of Example 5 but by means of a catalytic systemcontaining 2.1 mmol (240 mg) of TEAL (compound b) and 42 mg of compound(a1) described in Example 4, i.e. 0.19 mmol of TiCl₃.

This test produces a sticky, non-handleable polymer with an activity of5971.

It can be deduced from a comparison of Examples 3 to 9 with Example 10Rthat the presence, in the catalytic systems according to the invention,of the organic oxygenated silicon compound leads to the production ofstereospecific polymers.

EXAMPLES 11 to 15R

These examples are intended to illustrate the catalytic systemsaccording to the invention containing a compound (a2) as solid based oncomplexed titanium trichloride of δ crystalline form. Examples 11, 12and 14 are carried out according to the invention and Examples 13R and15R are given by way of comparison.

EXAMPLES 11

A--Preparation of the Catalytic Solid [compound (a2)]

The composition (0) is obtained by mixing, under an inert atmosphere andat 50° C., 800 ml of Isopar H (a mixture of aliphatic hydrocarbonsboiling at 175° C. marketed by Exxon Chemicals), 170 ml of DEAC and 82ml of isoamyl alcohol. This composition (0) of empirical formulaAlEt₁.45 (OR⁴)₀.55 Cl, where R⁴ represents an isoamyl radical, is storedat room temperature and under a nitrogen purge for 16 hours before beingused.

1 l of Isopar H and 150 ml of TiCl₄ are introduced into a dry 5-lreactor equipped with a stirrer having a blade rotating at 220 rev/min.While maintaining this TiCl₄ solution at 30° C., 690 ml of DIAE areslowly introduced (30 minutes) followed by 970 ml of the composition (0)described above. Introduction of the composition (0) takes place over 60minutes. After having reduced the stirring rate to 85 rev/min, 450 ml ofTiCl₄ are introduced over 20 minutes while increasing the temperature inorder to reach 100° C. after 15 minutes. The suspension is maintained at100° C. for 2 hours and the solid formed is isolated by settling andthen washed 7 times with 2 1 of dry hexane.

This purplish-coloured catalytic solid contains, per kg, 830 g of TiCl₃,1 g of aluminium and 58 g of DIAE; its IPV is 0.095 cm³ /g.

All of this solid (i.e. approximately 317 g of solid based on complexedTiCl₃) is suspended in 1.8 l of hexane at 30° C., with stirring at 150rev/min.

780 ml of a hexane solution containing, per litre, 80 g of DEAC and 176g of Irganox 1076 are slowly introduced (30 minutes) and then 240 ml ofpropylene over 30 minutes The suspension is kept stirring for 30additional minutes.

After settling, the resulting prepolymerised catalytic solid is washedwith dry hexane, with resuspension of the solid, and then dried bypurging with nitrogen in a fluidised bed for 2 hours at 70° C.

The solid thus obtained contains 535 g of TiCl₃, 18 g of DIAE and 228 gof prepolymerised propylene.

It is observed that this particularly simple preparation of compound (a)takes place in a single stage.

B--Polymerisation of Propylene in Suspension in the Liquid Monomer

The following are introduced, under purging with dry nitrogen, into a 5l autoclave which has been dried beforehand:

228 mg (2 mmol) of TEAL (in the form of a solution in hexane containing200 g/l) marketed by the firm Schering;

202.8 mg of DIBDMS (in the form of a solution in hexane containing 0.384mol/l);

67.7 mg of compound (a2) as prepared above;

a hydrogen pressure of approximately 1 bar;

3 1 of liquid propylene;

so that the molar ratio of the aluminium of TEAL to the titanium ofcompound (a2) is equal to 8.5 and that the molar ratio of the aluminiumof TEAL to the silicon of DIBDMS is equal to 2.

The reactor is maintained at 65° C. with stirring for 4 hours. Afterdegassing the excess propylene, there is recovered, with an activity of2673, a polymer with an AD of 343 additionally having an MFI of 6, anfTri of 92 and containing 64.5 ppm of chlorine.

EXAMPLE 12

This example illustrates the polymerisation of propylene maintained inthe gaseous state. The catalytic solid based on complexed titaniumtrichloride of δ crystalline form [compound (a2)] is obtained as inExample 11.

The following are introduced, under a stream of nitrogen and withstirring, into a 5 l autoclave used according to Example 1, Part B:

106 mg (0.93 mmol) of TEAL;

38 mg (0.19 mmol) of DIBDMS;

90 mg of compound (a2) as prepared above, i.e. 48 mg of TiCl₃ ;

1 l of liquid propylene.

The temperature is then raised to 50° C. and polymerisation is carriedout under these conditions for 10 minutes. The autoclave is thendegassed to a pressure of 11 bars absolute while being heated to 75° C.At this temperature, hydrogen and then propylene in the gaseous stateare introduced consecutively into the autoclave until a total pressureat the temperature under consideration of 20 bars absolute is reached.After polymerising for 3 hours under these conditions, the reaction isstopped by introduction of 25 ml of a 1 mol/l sodium hydroxide solution.

The activity of compound (a2) is 2870; the AD of the polymer is 343, itsMFI is 0.83 and its fTri is 92.

EXAMPLE 13R

This example illustrates polymerisation of propylene in the gaseousphase by means of a catalytic system containing 60 mg of a compound (a2)as described in Example 11 and 250 mg of DEAC.

The polymerisation test carried out under the conditions of Example 12leads, with an activity of 1833, to a polymer containing 42 ppm oftitanium and 540 ppm of chlorine and whose other characteristics are:

AD=344;

MFI=6;

fTri=95.

Comparison of Example 13R with Example 12 carried out according to theinvention shows again that the catalytic systems according to theinvention are particularly active and that they lead to polymers whichare particularly poor in chlorine.

EXAMPLE 14

The catalytic solid based on complexed titanium trichloride of δcrystalline form used in the catalytic system of this example is acompound (a2) deposited in a support.

A--Preparation of Compound (a2)

The composition (0) is obtained by successive introduction, into a 1litre, round-bottomed flask purged beforehand with nitrogen, of 300 mlof Isopar H, 43.2 ml of DEAC and 20 ml of Al(OR⁴)EtCl, where R⁴represents the isoamyl radical (obtained beforehand by equimolar mixingof DEAC and isoamyl alcohol).

1600 ml of Isopar H, 200 ml of TiCl₄, 230 ml of DIAE and 310 g of asilica support (marketed by the firm Grace under the name SG 532) aresuccessively introduced into a 5 litre autoclave, conditioned undernitrogen, equipped with a stirrer having a blade rotating at 250rev/min. While maintaining the suspension at 30° C., 363 ml of thecomposition (0) described above are added thereto over 1 hour. Thetemperature is then increased to reach 100° C. after 1 h.

The reaction mixture is maintained at this temperature for 2 hours andis then brought back to room temperature.

780 ml of a hexane solution containing, per litre, 80 g of DEAC areintroduced slowly (30 minutes), followed by 240 ml of propylene over 30minutes. The suspension is kept stirring for 30 additional minutes.

After settling, the resulting prepolymerised catalytic solid is washedwith dry hexane, with resuspension of the solid after each washing, andthen dried by purging with nitrogen in a fluidised bed for 2 hours at70° C. This compound (a2) contains, per kg, 341 g of TiCl₃. Its IPV is0.08 cm³ /g.

B--Polymerisation of Propylene in the Gaseous Phase

When subjected to a polymerisation test identical to that described inExample 12, a catalytic system containing 82 mg (0.72 mmol) of TEAL,36.7 mg of DIBDMS and 98.5 mg of this compound (a2) leads with anactivity of 2199 to a polymer having an AD of 413, a non-measurable MFIand an fTri of 93.

EXAMPLE 15R

Example 15R illustrates the polymerisation of propylene under conditionsidentical to those of Example 10R but by means of compound (a2) preparedas described in Example 14.

The catalytic system used contains 1.9 mmol of TEAL and 69.7 mg ofcompound (a2), i.e. 23.7 mg of TiCl₃.

This test produces, with an activity, of 3981, a sticky non-handleablepolymer.

Comparison of Examples 11, 12 and 14 with Example 15R makes it possibleto reveal the possible role played in the catalytic systems according tothe invention, by the organic oxygenated silicon compound.

EXAMPLE 16

This example illustrates the polymerisation of propylene in an inerthydrocarbon diluent (hexane) by means of a catalytic system containing acompound (a1) prepared as in Example 3, TEAL anddicyclopentyl-dimethoxysilane (DCPDMS) as compound (c).

Polyymerisation is carried out according to the following procedure.

The following are introduced, under purging with dry nitrogen, into a 5l autoclave which has been dried beforehand:

1 l of hexane;

157 mg of TEAL;

153 mg of DCPDMS;

48 mg of compound (a1);

The Al/Ti and Al/Si molar ratios are respectively equal to 7 and to 2.

The temperature being raised to 70° C., there are successivelyintroduced:

a hydrogen pressure of approximately 1 bar; and

a propylene pressure of 20 bars

before the polymerisation is carried out at this temperature whilemaintaining the pressure constant by supplying propylene.

After 3 hours, polymerisation is stopped by addition of 250 ml of watercontaining 25 mmol of sodium hydroxide. The polymer is collected in theform of a suspension which is filtered. The solid polymer fraction isdried and the polymer fraction which is soluble in the hexane ofpolymerisation is recovered by evaporation.

The polymer thus obtained has an AD of 499 and an MFI of 1.1. Theactivity of compound (a1) in this test is 3393. The polymer fractionwhich is soluble in the hexane of polymerisation is 1% by weight withrespect to the total weight of polymer formed.

We claim:
 1. A catalytic system for the polymerisation of α-olefin,comprising:(1) a solid based on complexed titanium trichloride of δcrystalline form having an internal pore volume from 0.02 to 0.4 cm³ /ggenerated by pores having radii from 1,000 to 15,000 Å, free ofmagnesium, obtained by heat treatment, in the presence of a halogenatedagent, of a liquid resulting from bringing TiCl₄, pretreated with anelectron-donating compound, into contact with a composition of theformula

    AlR.sub.p Z.sub.q X.sub.3-(p+q)

in whichR represents a hydrocarbon radical containing from 1 to 18carbon atoms, Z is selected from the group consisting of --OR⁴, --SR⁴and --NR⁴ R⁵ in which R⁴ and R⁵ each represent a hydrocarbon radical ora hydrogen atom, X represents a halogen atom, p is any number such that0<p<3, q is any number such that 0<q<3, the sum (p+q) being such that0<(p+q)≦3 (2) an organoaluminium compound selected from thenon-halogenated organoaluminium compounds of formula

    AlR.sub.m Y.sub.3-m

whereR represents a hydrocarbon radical, containing from 1 to 18 carbonatoms, Y represents a group selected from the group consisting of --OR¹,--SR¹, and --NR¹ R² in which R¹ and R² each represent an identical ordifferent hydrocarbon radical selected from the group consisting ofalkyl, aryl, arylalkyl, alkylaryl and cycloalkyl radicals, and m is anumber such that 0<m≦3 (3) an organic oxygenated silicon compoundselected from the group consisting of compounds of the formula:

    R'.sub.n Si(OR").sub.4-n

in which [R¹ ] R' represents a hydrogen atom or a hydrocarbon radicalcontaining from 1 to 20 carbon atoms, with the proviso that at least oneR' is selected from the group consisting of alkyl radicals andcycloalkyl radicals, said radicals containing at least one secondary ortertiary carbon atom, R" represents a hydrocarbon radical containingfrom 1 to 3 carbon atoms, n is 2 or 3,said organoaluminium compound (2)having a molar ratio of aluminium to silicon of said organic siliconcompound from 0.1 to 50 and said organoaluminium compound (2) having amolar ratio of aluminium to titanium of said titanium trichloride of δcrystalline form from 1 to
 50. 2. The catalytic system according toclaim 1, wherein the non-halogenated organoaluminium compound isselected from the group consisting of trialkylaluminiums and theirmixtures.
 3. The catalytic system according to claim 1, wherein theorganic oxygenated silicon compound is selected from the groupconsisting of dimethoxy- and diethoxysilane, said silicon compoundsubstituted by at least one radical selected from the group consistingof an alkyl radical and a cycloalkyl radical, said radical containing asecondary or tertiary carbon atom in the α, β, or γ position.
 4. Thecatalytic system according to claim 1, wherein the organic oxygenatedsilicon compound is chosen from diisobutyldimethoxysilane, di(tertbutyl)dimethoxysilane, diisopropyldimethoxysilane,dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane orisobutylmethyldimethoxysilane.
 5. The catalytic system according toclaim 1, wherein the solid based on titanium trichloride of δcrystalline form is obtained by adding to the medium for the preparationof the said solid, at any time, an organic or inorganic support (S)selected from the group consisting of the preformed polymers, the oxidesof silicon, aluminium, magnesium, titanium or zirconium, and mixtures ofthese oxides.
 6. The catalytic system according to claim 1, wherein themolar ratio of the aluminium of the non-halogenated organoaluminiumcompound to the titanium of the solid based on complexed titaniumtrichloride of δ crystalline form varies from 1.5 to
 25. 7. Thecatalytic system according to claim 1, wherein the molar ratio of thealuminium of the non-halogenated organoaluminium compound to the siliconof the organic oxygenated silicon compound varies from 1 to
 20. 8. Acatalytic system for the polymerisation of α-olefin, comprising:(1) asolid based on complexed titanium trichloride of δ crystalline formhaving an internal pore volume from 0.02 to 0.4 cm³ /g generated bypores having radii from 1,000 to 15,000 Å, free of magnesium, obtainedby heat treatment, in the presence of a halogenated agent, of a liquidresulting from bringing TiCl₄, pretreated with an electron-donatingcompound, into contact with a composition of the formula:

    AlR.sub.p Z.sub.q X.sub.3-(p+q)

in whichR represents a hydrocarbon radical containing from 1 to 18carbon atoms, Z is selected from the group consisting of --OR⁴, --SR⁴,and --NR⁴ R⁵ in which R⁴ and R⁵ each represent a hydrocarbon radical ora hydrogen atom, X represents a halogen atom, p is any number such that0<p<3, q is any number such that 0<q<3, the sum (p+q) being such that0<(p+q)≦3 (2) an organoaluminium compound selected from thenon-halogenated organoaluminium compounds of formula

    AlR.sub.m Y.sub.3-m

whereR represents a hydrocarbon radical, containing from 1 to 18 carbonatoms, Y represents a group selected from the group consisting of --OR¹,--SR¹, and --NR¹ R² in which R¹ and R² each represent an identical ordifferent hydrocarbon radical selected from the group consisting ofalkyl, aryl, arylalkyl, alkylaryl and cycloalkyl radicals, and m is anumber such that 0<m≦3, and (3) diisobutyldimethoxysilane.
 9. Acatalytic system for the polymerisation of an α-olefin, comprising:(1) asolid based on complexed titanium trichloride of δ crystalline formhaving an internal pore volume from 0.02 to 0.4 cm³ g generated by poreshaving radii from 1,000 to 15,000 Å, free of magnesium, obtained by heattreatment, in the presence of a halogenated agent, of a liquid resultingfrom bringing TiCl₄, pretreated with an electron-donating compound, intocontact with a composition of the formula

    AlR.sub.p Z.sub.q X.sub.3-(p+q)

in whichR represents a hydrocarbon radical containing from 1 to 18carbon atoms, Z is selected from the group consisting of --OR⁴, --SR⁴,and --NR⁴ R⁵ in which R⁴ and R⁵ each represent a hydrocarbon radical ora hydrogen atom, X represents a halogen atom, p is any number such that0<p<3, q is any number such that 0<q<3, the sum (p+q) being such that0<(p+q)≦3 (2) an organoaluminium compound selected from thenon-halogenated organoaluminium compounds of formula

    AlR.sub.m Y.sub.3-m

whereR represents a hydrocarbon radical, containing from 1 to 18 carbonatoms, Y represents a group selected from the group consisting of --OR¹,--SR¹, and --NR¹ R² in which R¹ and R² each represent an identical ordifferent hydrocarbon radical selected from the group consisting ofalkyl, aryl, arylalkyl, alkylaryl and cycloalkyl radicals, and m is anumber such that 0<m≦3, and (3) dicyclopentyldimethoxysilane.
 10. Acatalytic system for the polymerization of an α-olefin, comprising:(1) asolid based on complexed titanium trichloride of δ crystalline formhaving an internal pore volume from 0.02 to 0.4 cm³ /g generated bypores having radii from 1,000 to 15,000 Å, free of magnesium, obtainedby heat treatment in the presence of a halogenated agent, of a liquidresulting from bringing TiCl₄, pretreated with an electron-donatingcompound, into contact with a composition of the formula

    AlR.sub.p Z.sub.q X.sub.3-(p+q)

in whichR represents a hydrocarbon radical containing from 1 to 18carbon atoms, Z is selected from the group consisting of --OR⁴, --SR⁴,and --NR⁴ R⁵ in which R⁴ and R⁵ each represent a hydrocarbon radical ora hydrogen atom, X represents a halogen atom, p is any number such that0<p<3, q is any number such that 0<q<3, the sum (p+q) being such that0<(p+q)≦3 (2) a non-halogenated organoaluminium compound selected fromthe trialkylaluminiums in which the alkyl radicals contain more than twocarbon atoms (3) an organic oxygenated silicon compound selected fromthe group consisting of compounds of the formula:

    [R.sup.1 ]R'.sub.n Si(OR").sub.4-n

in which R' represents a hydrogen atom or a hydrocarbon radicalcontaining from 1 to 20 carbon atoms, with the proviso that at least oneR' is selected from the group consisting of alkyl radicals andcycloalkyl radicals, said radicals containing at least one secondary ortertiary carbon atom, R" represents a hydrocarbon radical containingfrom 1 to 3 carbon atoms, n is 2 or 3said organoaluminium compound (2)having a molar ratio of aluminium to silicon of said organic siliconcompound from 0.1 to 50 and said organoaluminium compound (2) having amolar ratio of aluminium to titanium of said titanium trichloride of δcrystalline form from 1 to 50.